Disk-based backup and remote disk-based data backup have become important tools for companies that want to get their data offsite but have short recovery time requirements. Pierre Dorion, data center practice director at Long View Systems Inc., discusses using disk-based backup for disaster recovery in this FAQ. His answers are also available as an MP3.

Disk-based backup and remote disk-based data backup have become important tools for companies that want to get their data offsite but have short recovery time requirements. Pierre Dorion, data center practice director at Long View Systems Inc., discusses using disk-based backup for disaster recovery in this FAQ. His answers are also available as an MP3 below.

Also, there's no media handling with offsite backup, so with tape out of the picture, we have the ability to start using replication technologies to send data across the wire instead of having to rely on physical tape movements. Also, disks are random-access devices, so they have no mount points. When you're using a tape, you have to wait for the media and the tape drive before you can access the data, whereas with disk, once the application accesses the data, it opens up multiple access streams. Offsite disk backup has the big advantage to leverage replication, too, but technologies such as snapshots and block-level backups can also capture a portion of the data that's changed. One downside to consider about offsite backup is that it costs more than using tape.

There are two different types of replication due to latency issues. Latency issues come about if there is network connectivity between two locations. The longer the distance between locations, the more hops you may run into, especially in the IP replication over an IP network. A good example of latency is when you're trying to look at the properties of a file on a file server. Although you aren't transferring the file, just the properties, there's a delay in getting that information. So these latency issues usually force people to move to asynchronous replication, which means you aren't gathering a simultaneous copy. A lot of companies are implementing a local synchronous replication, so they can obtain a backup copy immediately, and then with that local copy, you can create a remote copy asynchronously.

WAN optimization eliminates redundant transmissions of data. It stages data to local caches and compresses it. Furthermore, there's a data deduplication element that eliminates the transfer of redundant data across a WAN. With deduplication, once it identifies something it already has, it will just send a reference to it instead of the entire byte sequence, which allows you to send a lot less data across the wire, while keeping the transmission coherent. The compression aspect of WAN optimization will look for data patterns that can be represented more efficiently. So deduplication and compression are combined. Essentially, it allows you to send a lot more information across the WAN without using a lot of bandwidth by optimizing what you are sending.

A lot of deduplication technologies are replication capable. By replicating deduplicated data, network bandwidth requirements are reduced by copying or replicating a reduced data set across the network. In the end, when data deduplication is combined with WAN optimization, you can significantly reduce your data stream to two locations.

Some people confuse CDP with mirroring, or your traditional data replication. Continuous data protection is a point-in-time copy. Any kind of traditional backup will do a point in time copy whether it's to tape or disk. At the other extreme, mirroring is a constant copy of all the changes that are made to the data. The problem with mirroring is that if the original copy is corrupted, the replicated copies will also be corrupted. CDP, on the other had, captures every bit of info it changes, and allows the user to create certain recovery points as opposed to traditional backup where you only have one recovery point. In the example of corrupted data, CDP gives the user the ability to roll back certain changes to the point where the data was valid.

Who should use this? These technologies are meant for people who need continuous protection, but also need to recover data at a certain point in time. It really depends on how your recovery time objectives (RTOs) are defined. If you have very stringent requirements and have the ability to roll back in a granular fashion, CDP is better than mirroring, which has its limitations in the sense that it copies blindly without knowing if the data at the source is usable or not.

E-Chapter

E-Chapter

0 comments

E-Mail

Username / Password

Password

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy